From ec08a4a2810af6c6ae02e1aaa622676887f6456e Mon Sep 17 00:00:00 2001
From: lisyarus <lisyarus@gmail.com>
Date: Wed, 22 Dec 2021 20:35:21 +0300
Subject: [PATCH] Add util::updater and smooth_updater

---
 .../include/psemek/util/smooth_updater.hpp    | 67 +++++++++++++++++++
 libs/util/include/psemek/util/updater.hpp     | 14 ++++
 2 files changed, 81 insertions(+)
 create mode 100644 libs/util/include/psemek/util/smooth_updater.hpp
 create mode 100644 libs/util/include/psemek/util/updater.hpp

diff --git a/libs/util/include/psemek/util/smooth_updater.hpp b/libs/util/include/psemek/util/smooth_updater.hpp
new file mode 100644
index 00000000..aea3fe28
--- /dev/null
+++ b/libs/util/include/psemek/util/smooth_updater.hpp
@@ -0,0 +1,67 @@
+#pragma once
+
+#include <psemek/util/updater.hpp>
+
+#include <cmath>
+
+namespace psemek::util
+{
+
+	template <typename Time, typename Value = Time>
+	struct smooth_updater
+		: updater<Time>
+	{
+		smooth_updater(Value & value, Time speed)
+			: value_(value)
+			, target_(value)
+			, speed_(speed)
+		{}
+
+		template <typename H>
+		smooth_updater & operator = (H new_value)
+		{
+			target_ = new_value;
+			return *this;
+		}
+
+		template <typename H>
+		smooth_updater & operator += (H new_value)
+		{
+			target_ += new_value;
+			return *this;
+		}
+
+		template <typename H>
+		smooth_updater & operator -= (H new_value)
+		{
+			target_ -= new_value;
+			return *this;
+		}
+
+		template <typename H>
+		smooth_updater & operator *= (H new_value)
+		{
+			target_ *= new_value;
+			return *this;
+		}
+
+		template <typename H>
+		smooth_updater & operator /= (H new_value)
+		{
+			target_ /= new_value;
+			return *this;
+		}
+
+		void update(Time dt) override
+		{
+			using std::lerp;
+			value_ = lerp(target_, value_, std::exp(- dt * speed_));
+		}
+
+	private:
+		Value & value_;
+		Value target_;
+		Time speed_;
+	};
+
+}
diff --git a/libs/util/include/psemek/util/updater.hpp b/libs/util/include/psemek/util/updater.hpp
new file mode 100644
index 00000000..102c0c13
--- /dev/null
+++ b/libs/util/include/psemek/util/updater.hpp
@@ -0,0 +1,14 @@
+#pragma once
+
+namespace psemek::util
+{
+
+	template <typename Time>
+	struct updater
+	{
+		virtual void update(Time dt) = 0;
+
+		virtual ~updater() {}
+	};
+
+}